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11
INSTALLATION
 
A. HANDLING FREON 12
 
11A1. Precaution. Since Freon 12 is practically odorless and nontoxic, it is not necessary to wear a gas mask when servicing equipment that contains it. However, it is essential that proper protection be afforded the eyes by the use of goggles or large-lensed spectacles to eliminate the possibility of liquid Freon 12 coming in contact with the eyes and causing injury by freezing the tissues of the eyes. This protection is necessary and should be taken whenever loosening a connection on a system in which Freon 12 is confined.   11A2. Remedies. If liquid Freon 12 should come in contact with the eyes, the person suffering the injury should be taken at once to an eye specialist. Avoid rubbing or irritating the eyes and give the following first-aid treatment immediately:

1. Irrigate the eyes with drops of sterile mineral oil.

2. If irritation continues, wash the eyes with weak boric acid solution or sterile salt solution not exceeding 2 percent sodium chloride (common table salt).

 
B. MOISTURE, DIRT, AND AIR
 
11B1. Important. In a refrigerating or air conditioning system there is no room for any thing but the refrigerant and oil inside the compressors, condensers, receivers, and evaporators, or in the tubing, fittings, or valves that connect the various pieces of apparatus.

The refrigerant used in these systems, Freon 12, is a powerful solvent that readily removes from the inside of pipes, valves, and fittings, any dirt, scale, sand, or moisture that has been allowed to remain in them during installation. These foreign substances are soon swept along with the suction gas into the compressor, and are a distinct hazard to the bearings, pistons, cylinder walls, valves, and lubricating oil. Scoring of moving parts frequently occurs when the compressor is run for the first time, starting with minor scratches that increase progressively until they seriously affect the operation of the compressor, eventually rendering it unfit for further use.

If the system is carefully and properly installed, excluding all foreign matter, the

  compressor operates satisfactorily and gives many years of service free of trouble.

Most service troubles are caused by lack of adequate precautions during erection and installation. It is of extreme importance that the installation man know the necessity of keeping the system internally clean, as well as the use of the proper material for tubing, joints, and fittings.

The condition of the compressor lubricating oil, especially its color and appearance, is a good indication of the degree of contamination of the system.

The installation of some systems may be complicated by the many trades involved and the unavoidable delays that may occur between the start and the completion of the installation. Therefore, extraordinary precautions must be taken to prevent the entrance of foreign matter into any part of the system. It is most important that all openings in tubing, piping, fittings, and other parts of the system be promptly sealed during the time that no work is being performed on them.

 
C. INSTALLATION OF UNITS
 
11C1. Installation of the condensers, evaporators, receivers, and auxiliary equipment. These major units are generally located or installed prior to the running of connecting mains. This part of the installation should   conform to the plans and specifications for the individual system involved.

CAUTION. All openings on these major units must remain sealed until the connections to them are actually made.

 
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D. INSTALLATION OF REFRIGERANT MAINS
 
11D1. Copper tubing and copper pipe specifications. Copper tubing and copper pipe should conform to the standards of the Navy specifications. It should be cleaned, deoxidized, dehydrated, and sealed by the manufacturer before shipment, and thereafter should remain sealed at all times. When it becomes necessary to cut sections of its seal all open ends of the remaining portions.

11D2. Stock tubing. When stock tubing or pipe must be used, the following instructions should be carefully observed.

With a strong blast of dry air, thoroughly blow out each length or coil of tubing. With a cloth swab attached to copper wire, pull the swab back and forth in the tube until it is clean and shiny, then seal the ends of the tube. A swab for this purpose is easily made by kinking the copper wire or coiling it like a corkscrew and winding a piece of flannel around it tightly so that it passes through the tube with just enough friction to clean the tube but not to become lodged. Do not use waste or other material that might leave lint.

After each tube or pipe has been thus cleaned, the two open ends should be sealed against the entrance of moisture or dirt by covering the ends with a small piece of canvas taped securely in place.

11D3. Cutting tubing and pipe. In cutting copper tubing or pipe, care must be exercised to prevent filings or cuttings from entering the pipe. Some effective means should be used to clean out the small particles of copper that do enter the tube or pipe. Finely divided copper that can pass through the suction strainer collects in the compressor crankcase lubricating oil, where, together with small quantities of air and moisture, it may promote oil gumming and sludging and often cause chemical reaction. These particles may also be carried by the lubricating oil to the seal, bearings, and cylinder walls, and thus cause seal and bearing failure, or scoring of the cylinder walls and pistons.

When cutting copper tubing with a wheel cutter, it is extremely important to use only sharp wheels. The soft copper wears the edge of these wheels more quickly than might be

  expected; therefore, the condition of the wheels must be checked regularly. Always ream the tube ends to remove the burrs. Even with sharp wheels, great care must be taken to prevent crushing or denting of the tubing. With a dull wheel, considerable pressure is necessary to cut the tube; this may result in the formation of a heavy burr, or neck, at the cut. Also, the outside of the tubing is upset or bulged a little at the cut. This must be dressed with a sharp fine file to permit the tubing to enter the fitting freely;

When cutting copper tubing with a hacksaw, it is important to use sharp blades; blades with 32 teeth per inch give the best results. Dull blades tear the tubing and leave troublesome burrs. The tubing must be cut square, and all burrs removed with a sharp fine file from both inside and outside. Hold the tubing so that the filings will not drop in the length of tubing where they cannot be removed.

11D4. Preparing ends of tubing and pipe joints. When making soldered and brazed joints, it is necessary to brighten the ends of the tubing or pipe to make a good bond. This brightening should be accomplished with a wire brush or with crocus cloth.

Do not under any circumstances use sand paper, emery cloth, or steel wool for dressing the ends of tubing or pipe, as this material is certain to enter the tubing or pipe and is eventually carried back to the crankcase of the compressor, where it may be a direct cause of seal, bearing, cylinder wall, or piston failure.

11D5. Use of flux. Under no consideration should acid be used in soldering. Care must be exercised to choose a type of flux having a residual substance that does not form an acid. Care must also be exercised while making the joints to prevent flux from entering and piling up on the inside of the tubing or pipe, since it would eventually be washed back to the compressor crankcase. Fittings that are not properly sized and that fit imperfectly are difficult to solder or braze. Consequently, there is danger of piling up filler metal as well as flux inside the tubing or pipe.

11D6. Making soldered or brazed joints. A soldered joint, as well as a brazed joint, requires

 
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a temperature sufficiently high to cause oxidation within the tubing or pipe, and consequently some means must be provided to maintain a neutral atmosphere within the tube or pipe. Oil pumped nitrogen gas should be blown through the tubing or pipe being soldered or brazed, and continued after the joint is made until the copper is brought down below its oxidation temperature.

Copper oxide is one of the substances that, in combination with air and moisture, produces gumming and sludging of the lubricating oil and causes a chemical reaction such as copper plating of the working parts of the compressor.

If a system has once been charged with Freon 12 refrigerant and develops a leak, it is necessary to blow out any traces of the refrigerant vapor and oil from that part of the system before attempting to repair the leak.

The temperature level necessary in soldering is sufficient in the presence of copper to cause the disintegration of Freon 12, creating harmful acids and general contamination of the system.

Oil pumped nitrogen gas should be used to blow out the section to be repaired. A small amount of this gas should be permitted to flow during the soldering to create an inert atmosphere.

When making the soldered joint between tubing and valves, especially those of the diaphragm packless type, it is important to protect the diaphragm and the composition seat disk in the lower stem from damage caused by excessive heat. To provide maximum protection to internal parts, the following instructions should be carefully followed. The time that heat is being applied should be a matter of seconds.

Preliminary to heating the connection, open the valve wide by turning the handwheel counterclockwise until the stem is all the way back, then turn the handwheel forward clock wise about 1/4 turn. This moves the lower stem and disk away from contact with the valve body and thus minimizes the danger of heat being transferred to the valve seat. The steps in the soldering operation are:

1. Thoroughly clean the end of the tubing and the socket connection in the valve body.

2. Apply a thin coat of properly mixed high

  quality noncorrosive flux to the end of the tubing and the valve body socket.

3. Insert the tubing in the valve socket until it is tightly seated against the shoulder.

4. To preheat the tubing, apply the torch in a sweeping, fanning motion. It is necessary to heat about 2 inches of tubing beyond the valve port.

5. Following the preheating stage, gradually fan the torch flame toward the valve port.

6. Quickly fan the flame around the end of the valve port. This heats the valve port and the tubing to the desired temperature.

7. After the flux has melted, touch the joint with the soldering wire. If the joint is hot enough, the wire melts, flows, and seals the joint.

8. After the solder has been applied, quickly apply a wet cloth over the valve body and the soldered joint.

11D7. Making SAE flare joints. Before preparing the flare, be sure to slip the flare nut over the tube end. To make a satisfactory flare joint, the flare must be as full as possible but small enough to clear the threads of the flare nut. The flare must be of uniform thickness, smooth, and free from tool marks, splits, ridges, high spots, and so forth. To get a full flare, the tubing must be cut square; to get a smooth flare, the burrs must be removed and new filings cleaned out of the inside of the tube.

The flare seat of the fitting connector must be bright and free from dents or scratches. If it has been damaged in any way, scrap the fitting. Do not attempt to correct a damaged flare seat by filing or sandpapering. The flare seat of the fitting and the inside of the tubing flare must be clean and dry when they are connected.

The SAE flare can best be made by the use of a swivel-headed flaring tool that remains stationary and does not tear or scar the face of the flare in the tubing. Do not use oil as a lubricant on the face of the flare, either in making up the flare or in drawing it up. It is impossible to remove oil from the surface of the flare by drawing up the flare joint. This oil would eventually be dissolved by the Freon 12 in the system, causing a leak at this joint. These joints must be clean and free from foreign matter.

 
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SAE fittings are, shipped and packed with special protective caps that should not be removed until making up the joint, otherwise the faces are easily damaged.

a. Tightening flare joints. When tightening a flare joint, always use two wrenches: one to turn the nut, and the other to hold the fitting, valve, or flange. If only one wrench is used, the chances are that the connecting tubing, the joint, the fitting, or the flange will be strained, resulting in a leak.

The required pull on the wrenches for tightening the various sizes of flare joints is a matter of experience. The pull necessary for a 5/8-inch joint is obviously too great for a 3/8-inch joint.

11D8. Bending copper tubing or pipe. CAUTION. Do not use rosin, sand, or any other type of filler inside a piece of tubing or pipe in order to make a bend.

Bends can be made by various types of external forms or tools particularly designed for this kind of work. These tools may have a tendency to distort the tubing or pipe at the point of the bend from a true circular cross section; however, this slight distortion is not serious from the standpoint either of appearance or of pressure drop.

11D9. Cleaning copper tubing or pipe. In the event that the outside of the copper tubing or pipe is discolored and the specifications call for brightening such tubing, do not under any circumstances clean it with an acid bath. Such tubing or pipe should be installed as it is, and any brightening or polishing can be done

  externally by means of a wire brush or crocus cloth.

11D10. Securing and handling copper tubing or pipe. In general, the specifications for the installation call for proper securing, anchoring, or hanging of the suction and liquid lines. Care must be exercised to permit sufficient flexibility between the compressor and the first set of hangers or points at which the lines are secured, to permit a certain amount of freedom and relieve any possible strain in the joints of these lines at the compressor.

11D11. Copper tubing and pipe fitting specifications. The special type of copper tube or copper pipe fitting designed for refrigeration service differs from the ordinary plumbing type of fitting in that the tolerances are held much closer to permit tight capillary joints of the soldered and brazed type. In the event that only standard tubing is available, the joint section should be enlarged or decreased by a suitable tool.

In all cases, fittings should be of the forged type, to eliminate porosity. All SAE flared fittings should be of the forged brass type, as those machined from ordinary bar stock are not substantial and eventually succumb to what is known as season cracking. It must be remembered that such fittings are under a considerable load when drawn tight.

11D12. Use of thread compound. The use of thread compound is not recommended. Any threaded or screwed joints must be seal welded or silver brazed.

 
E. INSTALLATION OF THERMOSTATIC EXPANSION VALVE
 
11E1. Function of the thermostatic expansion valve. The thermostatic expansion valve is used to control the flow of liquid Freon 12 refrigerant to the evaporator. This device plays a most important part because it is absolutely necessary to control the flow of refrigerant, not only to obtain the proper amount of refrigeration in each evaporator, but also to prevent liquid refrigerant from flooding out of the evaporator and going to the compressor in liquid form. Liquid refrigerant flowing to the compressor can cause damage in several ways, one of which is to bring about a condition   wherein the lubricating oil is forced out of the compressor crankcase into the system. This results in the compressor operating without proper lubrication, damaging the cylinder walls, pistons, bearings, and seal.

The thermostatic expansion valve consists of the body housing, the operating mechanism, a capillary tube, and a thermal bulb. The thermal bulb is clamped to the suction line adjacent to the outlet of the evaporator in order to feel the temperature at this point. The thermal bulb is filled with a charge of liquid that is responsive to temperature change. The pressure

 
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from the liquid in the bulb actuates the needle valve controlling the flow of liquid refrigerant.

11E2. Application of heat for soldered or brazed joints. Before applying heat to make up soldered connections, remove the power assembly and all gaskets. Keep heat away from all parts except the main body inlet and outlet.

11E3. Attaching the thermal bulb to the evaporator suction line. It is absolutely necessary that the thermal bulb be clamped tightly to the suction line from the evaporator in order to respond quickly to temperature changes at this point, because it is this feature that causes the expansion valve to function properly. Special clamps are packed with the thermostatic expansion valve and must be used to fasten the thermal bulb. On pipe lines under 7/8-inch o.d., attach the bulb on top center of the pipe. On lines 7/8-inch o.d., or larger, attach the bulb about 45 degrees away from top center.

Clean the pipe or tubing thoroughly before attaching the remote bulb. Then draw up the clamp tight so that the bulb makes a firm positive contact with the suction pipe. It is also advisable to insulate both bulb and pipe together for a distance of at least 18 inches. Do not fasten the bulb on the suction line in a cold location immediately ahead of the point

  where the suction line enters a warm room, because heat from the warm room will reach the bulb by conduction and cause faulty thermo-valve action.

If the thermal bulb is not securely attached to the suction line with the thermal bulb clamp, erratic operation results. Liquid maybe flooded out of the evaporator and returned to the compressor, causing damage.

11E4. Locating the thermal bulb. It is preferable to place the thermal bulb as near the outlet of the evaporator and as high as possible on the suction line, using care to avoid placing it in any trapped portion.

In some cases, certain obstructions cannot be overcome and it may be necessary to run the suction line from the evaporator in as convenient a way as possible, resulting in traps which must be avoided when attaching the thermal bulb. Furthermore, the suction line at this point should be straight. Do not locate the thermal bulb at a point where the suction line is bent, as this results in poor contact.

CAUTION. The entire thermostatic expansion valve assembly, including the capillary tube and thermal bulb, must be treated as a delicate instrument as it will not withstand rough handling.

 
F. TESTING FOR LEAKS
 
11F1. Evacuating the system. CAUTION. Do not under any consideration use the condensing unit for evacuating the system. The condensing unit leaves the factory with the compressor absolutely clean and free of foreign matter. If the compressor were used in the evacuation process, foreign matter would be brought back from the evaporators and refrigerant mains and damage the compressor before it starts on its regular cycle of operation.

Evacuation of the system is accomplished by the following procedure:

1. It is necessary to use an auxiliary vacuum pump capable of pulling at least 29 inches of vacuum.

2. Connect the suction side of the vacuum pump to the liquid charging valve, allowing the pump to discharge to the atmosphere,

3. Open all valves on the system to be evacuated.

  4. Run the vacuum pump until the lowest vacuum possible is obtained; then stop the pump, and close the liquid charging valve.

The time required for this preparation varies with the capacity of the compressor and the amount of surface to be pumped out, but, in general, a few hours suffice.

If it is impossible to obtain a 29-inch vacuum, probably it is because of one of the following reasons:

a) Presence of excess moisture in the system.

b) Presence of absorbed refrigerant in the oil in the crankcase.

c) Leakage of air into the system. If there is a leak in the system, it should be found and stopped.

After the desired vacuum has been obtained, allow it to remain overnight. If the system has not lost more than 2 or 3 inches of vacuum

 
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by the next morning, it may be considered reasonably tight.

11F2. Charging the system with nitrogen gas and Freon 12 mixture for leak detection. After the preliminary evacuation, it is recommended that the system be tested for leaks by introducing sufficient Freon 12 refrigerant to raise the system pressure to approximately 10 psi; then test for leaks with the halide torch. If the system is found to be tight at this pressure, introduce sufficient oil pumped nitrogen gas to raise the system pressure to the required test pressure. The nitrogen gas drum should then have its connection broken from the system so that no accident may occur due to the building up of excessive pressure as a result of a leaky valve at the gas drum. The system should again be tested for leaks at the high-pressure level.

11F3. Use of oil. Oil should never be used in testing for Freon 12 leaks. Oil is unreliable because of the capacity of the oil for absorbing Freon 12. If a small leak should exist where oil has been applied, the Freon 12 is absorbed by the oil and shows no indication by bubbles until after the oil is saturated with Freon 12. Furthermore, if an attempt is made to test a leaky joint that has been tested previously with oil, using a halide torch, a false indication in the halide torch results because Freon 12 is released from the oil.

11F4. Use of soapsuds. A halide torch is so sensitive that, if there are any bad leaks, the atmosphere around the apparatus becomes so contaminated with Freon 12 that it is impossible to locate the source of the leak with the aid of the torch. This condition prevails especially if the apparatus is located in a small or poorly ventilated room. Under such conditions, the halide torch is of little value in discovering the exact location of the leak, and soapsuds must be used.

To prepare soapsuds for testing, use a soap and water solution of about the consistency of liquid hand soap, which lathers freely, or work up a lather on a wet brush by rubbing the brush on a cake of soap. A few drops of glycerine added to the solution make the lather remain wet longer. When applying the soap suds, paint the soap lather on the joint all the way around and examine the joint thoroughly

  for bubbles. When the joint is so located that a part of it is not visible, use a pocket mirror. It sometimes takes a full minute or more for bubbles to appear at a small leak. Questionable spots should be covered with lather and examined again.

11F5. Use of halide torch. Freon 12 leaks are detected by a specially designed torch known as a halide torch. (See Figure 11-1.) Atmosphere suspected of containing Freon 12 gas is drawn through an exploring hose into the burner by injector action. The air sample passes over a copper reactor plate in the burner chamber which is heated to incandescence by the flame. When Freon 12 gas is not present,

Figure 11-1. Halide torch.
Figure 11-1. Halide torch.

 
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the color of the flame is a faint blue, almost invisible in the flame shield. If even a minute trace of Freon 12 is present, the torch flame changes from its normal faint bluish color to a dull but unmistakable green as the air sample comes in contact with the reactor plate.

The shade of green depends upon the relative amount of Freon 12 present, being pale for small concentrations and deeper for heavier concentrations. Excessive quantities of Freon 12 color the flame a vivid purple, and may even extinguish it by crowding out the supply of oxygen in the air. A number of halide torches are available on the market, most of which use acetylene gas or alcohol as a fuel. The acetylene burning Prest-O-Lite torch manufactured by the Linde Air Products Company is supplied for most Navy installations.

11F6. Directions for using halide torch. Several precautions must be observed in using the Prest-O-Lite leak detector to obtain best results. They are:

1. Be sure the reactor plate is in place.

2. Adjust the flame low enough so that it does not extend beyond the top of the burner chimney. A small flame is much more sensitive than a large flame. If difficulty is experienced in lighting the torch with the small gas flow necessary, block the end of the exploring hose until the flame ignites, then gradually open.

3. If the flame persists in burning with a white or yellow color, the exploring tube is partially blocked with dirt and should be cleaned.

4. Try the torch in an atmosphere in which there is known to be a small amount of Freon 12, to make sure that it is finally working properly. Check to see that air is being drawn into the exploring tube, by holding the end of the tube to the ear from time to time.

5. Hold the exploring tube close to the joint

  being tested, to prevent dilution of the sample by stray air currents.

6. Move the end of the exploring hose slowly around each joint. There is a definite time lag between, the instant that the air enters the exploring hose and the time that it hits the reactor plate. Leak testing cannot be hurried.

7. If a green tinge is noted in the flame at any point, repeat the test in the same vicinity until the source of the Freon 12 is determined. Use soap bubbles if necessary to find the exact point at which a leak is occurring.

8. Do not use the torch in an atmosphere known to be heavy with Freon 12 as this tends to foul it.

11F7. Finding leaks. Always follow a definite order in testing for leaks, so that no joints are missed.

Find every leak. Even the smallest leak is not to be considered negligible. However insignificant the leak may seem, it eventually empties the system of its charge to the point of faulty operation. Because Freon 12 is practically odorless, the first indication is the loss of refrigerating effect. The extra time spent in testing all threaded, flared, soldered, and valve cap gasket joints made in the field, as well as the factory fabricated connection, is justified.

The system must never be recharged until all leaks are discovered and completely repaired. Upon locating one leak do not assume that it alone is responsible for the difficulty. Thoroughly retest the complete installation.

11F8. Procedure after system has been tested for leaks. After the system has been tested and found to be tight, it should be evacuated with the vacuum pump to 29 inches of vacuum, discharging the mixture of Freon 12 and nitrogen to the atmosphere. Make sure that the ventilating system is in proper operation during this procedure.

 
G. CLEANING REFRIGERANT MAINS, EVAPORATORS, AND AUXILIARY EQUIPMENT BEFORE OPERATION
 
11G1. Operation of compressor before cleaning the system. The compressor should not, under any circumstances, be operated until the system has been thoroughly cleaned by the special process described here. If it is necessary for any reason to check the operation   of the motor, the belt guard and the belts should be removed and the motor operated alone.

11G2. Necessity for system cleaner. Although every precaution is taken to keep the system absolutely clean during installation, a

 
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certain amount of foreign matter enters it, and this must be removed before the system is permitted to operate. Foreign matter can be successfully removed from the system by means of the York system cleaner, which is a special surge drum containing a filter, screen, and a large body of activated alumina dehydrating agent. The system cleaner is connected to the suction side of the system by means of a special adapter assembled in the suction strainer housing. This permits breaking into the system at this point without disturbing any other connection.

11G3. Connecting the York system cleaner. Connecting lines to and from the York system cleaner are attached to a special adapter that is temporarily assembled in the suction strainer housing. Suitable adapters are available for the various types and sizes of suction strainer housings.

The choice of connecting lines between the system cleaner and the adapter depends upon local conditions. Use flexible armored tubing or plain copper tubing. These lines should be selected as large in diameter as practical, taking into consideration the size of the openings in each adapter.

The system cleaner should be located as close as possible to the compressor.

The outlet of the adapter must be connected to the inlet of the system cleaner and the outlet of the system cleaner connected to the inlet of the adapter. For convenience of installation, the adapter is provided with two outlets. In addition to this, the adapter can be rotated in several positions.

The system cleaner may be installed at any time before final evacuation of the entire system. The suction and discharge stop valves of the compressor must remain closed up to this time, isolating both the compressor and the system cleaner.

11G4. Final evacuation. Before starting the system cleaner, the entire plant, including the compressor and system cleaner, should be evacuated with an auxiliary vacuum pump to at least 29 inches of vacuum.

11G5. Charging the refrigerant circuit with Freon 12 for system cleaning. Purge the flexible charging connection with Freon 12, then connect it to the charging valve. All

  valves on the circuit to be cleaned should be open, except the purge and drain valves. With water circulating through the condenser, charge the weighed amount of liquid Freon 12 into the system. Since the Freon 12 charge is adequately distilled by the cleaning process described in the following paragraphs, it should be allowed to remain in the system for the normal refrigerating cycle.

11G6. Cleaning procedure. Foreign matter that usually returns to a compressor is intercepted by the York system cleaner. The return of this foreign matter is accelerated by actually flushing Freon 12 in its liquid state through the evaporators, mains, and auxiliary parts, back into the cleaner.

All liquid refrigerant and vapor entering the York system cleaner must pass through a fine mesh screen, a cloth filter bag, and a relatively large charge of activated alumina. Therefore, removal of moisture, as well as other foreign matter, is effected. Liquid refrigerant passing through this part of the cleaner collects in the large sump at the bottom. Only pure dry refrigerant vapor is pumped from this sump to the compressor.

11G7. Step by step operation for cleaning. The compressor is now put in operation for the first time. Each individual evaporator circuit should be flushed out with liquid Freon 12 by warming the thermal bulb of the expansion valve and opening the hand bypass valve (if furnished). If a solenoid valve is in the liquid control circuit, make sure that its thermostat holds it open.

If several evaporator circuits are connected to one compressor, clean each circuit separately. Start work at the evaporator at the greatest distance from the compressor, mean while isolating the other evaporators. Proceed progressively toward the compressor with the cleaning of all the other evaporator circuits, thereby preventing foreign matter from being deposited in a cleaned evaporator.

Care must be taken that the level of liquid refrigerant in the York system cleaner is held sufficiently low so that it is not drawn into the compressor. This must be constantly observed through the sight glasses. It is necessary to provide heat at the bottom of the system cleaner by means of an electric

 
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hot plate, radiant heater, trip heater, or by standing the cleaner in a container of warm water.

In heating, care must be exercised not to create so violent an evaporation that spilling over of the liquid to the compressor results. The proper liquid level to insure that only vapor returns to the compressor is maintained by controlling the liquid through the evaporator, by throttling the stop valve on the inlet to the cleaner, or by controlling the heat applied to the cleaner.

The oil level in the compressor crankcase must be carefully watched and maintained at approximately its original height by the addition of pure clean compressor oil when necessary.

11G8. Maintenance of the York system cleaner. The filter cloth and screen should be cleaned by immersing in approved cleaning solvent after each complete system cleaning. Replacement of the charge of activated alumina depends upon the quantity of moisture removed from the system.

A certain amount of fine foreign matter and

  oil may collect in the bottom of the system cleaner shell. This should be washed out with approved cleaning solvent after each cleaning operation.

Activated alumina must always be kept tightly sealed to prevent absorption of moisture from the atmosphere.

The length of time required to clean each evaporator circuit varies, depending upon such factors as size and length of lines. The flushing procedure should be not less than one-half hour per evaporator circuit.

11G9. Removal of the York system cleaner. After cleaning the last evaporator circuit in each system, the compressor suction stop valve should be closed and the refrigerant remaining in the sump of the system cleaner should be pumped out, but not below atmospheric pressure.

The inlet and outlet valves of the system cleaner are then closed and the adapter is removed from the suction strainer body. Finally, the suction strainer cover plate is put in place.

 
H. ADDING AND REMOVING FREON 12
 
11H1. Charging Freon 12. To charge additional Freon 12 in the system, proceed as follows (NOTE. Observe and practice the precautions listed under Handling Freon 12 in Section 11A1):

1. If the Freon 12 charge has been lost, pump a vacuum on the entire system.

2. Mount the Freon 12 cylinder on a portable platform scale, preferably in an inclined position with its head lower than its base.

3. Connect the Freon 12 cylinder to the Freon 12 charging connection.

4. Slightly open the valve on the Freon 12 service cylinder, and test charging connections for leaks with soapsuds.

5. Open the charging valve and the Freon 12 cylinder valve, and charge in sufficient Freon 12 to create 60 pounds of pressure. In a new system or one in which there may be leaks, it is advisable to check all connections with the halide torch before adding any more Freon 12.

6. Close the liquid valve at the outlet of the receiver, run the compressor, and charge sufficient

  Freon 12 into the system. Be sure that the compressor suction, discharge stop valves, and the valve between the condenser and the receiver are open.

NOTE. When the system includes two compressors, condensers, and receivers, close both liquid valves at the outlet of the receivers, and run both compressors with suction and discharge stop valves open.

7. The liquid charging valve must be closed sufficiently to provide a pressure at the charging connection lower than the pressure in the Freon 12 cylinder, so that the Freon 12 will flow from the cylinder into the line. By observing the change in weight of the cylinder, the weight of charge added can be obtained.

11H2. Refrigerant charging connections. The charging valve, which may be of either the packless angle or globe type, is located in the liquid line between the receiver and the dehydrator.

The Freon 12 cylinder is preferably mounted on scales in an inclined position with the top

 
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lower than the base to enable the operator to determine accurately the amount of refrigerant charged into the system.

The charging connection consists of a flexible section with a 6-inch length of 3/8-inch o.d. copper tubing soldered to each end.

The flexible section is made up of a seamless bronze bellows tube, reinforced and protected on the outside by heavy bronze wire braid. The ends of the bellows tube and bronze wire braid are fitted with copper ferrules, to which are soldered the 6-inch lengths of copper tubing. The outer ends of these tubes are flared and fitted with standard 3/8-inch SAE flare nuts.

A 3/8-inch male SAE flare to 3/4-inch female pipe-threaded adapter is furnished for connecting to a standard Freon 12 cylinder valve.

11H3. Removing Freon 12. If a system has been overcharged with Freon 12 or if the charge is to be transferred from the system, proceed in the following manner:

1. Start the compressor and pump down the evaporator pressure to zero psi, with the liquid valve out of the receiver closed.

  2. Close the discharge stop valve and an liquid valves at the cooling coils.

3. Connect an empty Freon 12 cylinder to the liquid charging valve.

NOTE. Be sure that the cylinder is large enough to prevent danger of overfilling. Before connecting the cylinder to the Freon 12 system, set it in an ice-water bath to cool the cylinder thoroughly.

4. Open the liquid charging valve and the Freon 12 cylinder valve. Then slowly open the liquid outlet valve at the receiver. The cooled Freon 12 cylinder drains Freon 12 from the system until the pressure in the cylinder is equal to the pressure in the system. To remove the remaining Freon 12 from the system, it is necessary to use a second empty cold cylinder. The colder the cylinder, the less Freon 12 will remain in the system.

CAUTION. After disconnecting the Freon 12 cylinder from the system, weigh it to be certain that is has not been overcharged. The net and gross weights are stamped on the cylinder, and include the weight of the cast iron protecting cap.

 
I. FINAL ADJUSTMENTS
 
11I1. Final adjustment of stop valves and controls. After the system has been thoroughly cleaned, each evaporator circuit must be checked to make sure that the expansion valve thermal bulb is properly located and securely clamped to the suction line. If hand-operated bypass valves are furnished, they must be closed tightly and locked to prevent them from being opened except in case of emergency, and then only by authorized operators who realize the extreme danger of flooding liquid back to the compressor.

If a solenoid valve is in the liquid control circuit, make sure that its thermostat holds it open during the period of adjustment.

The condensing unit is now placed in operation and the suction pressure switch is blocked in the running position to insure continuous operation.

On air-cooled condensing units, the compressor discharge pressure should be maintained at approximately 150 psi during the final adjustment period, by controlling the air to the condenser.

  During the final adjustment period, the level of the oil in the compressor crankcase must be constantly observed as it may be pumped over to the evaporators faster than it is returned, until final adjustments are made and normal operating conditions are obtained.

CAUTION. If the oil level should fall below the bull's-eye, add oil temporarily. It may be necessary to withdraw some of the oil thus added when normal conditions prevail.

The condition of the compressor lubricating oil, especially its color and appearance, is a good indication of the effectiveness of the system cleaner. The color can be observed at the compressor crankcase bull's-eye, or a sample can be drawn off the crankcase drain valve and compared to new clean oil.

11I2. Adjustment of thermostatic expansion valves. To obtain full evaporator capacity and at the same time prevent liquid refrigerant from returning to the compressor, it is necessary that the proper superheat adjustment be made on each evaporator circuit. Navy specifications call for 10 degrees of superheat.

 
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Superheat means the difference in temperature between the liquid entering the evaporator circuit and the vapor leaving the evaporator circuit. This is best determined by the use of clip-on thermometers located on the tubing entering the evaporator circuit and the tubing leaving the evaporator circuit. These clip-on thermometers, to be effective, must be attached tightly against a clean bare spot on the tubing.

If the specifications call for insulation of any lines, this insulation should be applied before attempting to adjust the expansion valves. If the thermal bulbs are to be insulated, this also should be done before valve adjustment.

Thermostatic expansion valves for submarine installation are factory set for 10 degrees of superheat. The conditions of some installations may be such that 10 degrees of superheat are not accurately produced. Each evaporator circuit should therefore be separately checked, and if necessary, the expansion valve in the circuit adjusted. To change the superheat setting, remove the seal nut and manipulate the adjusting stem (see Figure 7-10). Turning the stem clockwise increases the superheat; turning the stem counterclockwise reduces the superheat.

When making the adjustment, observe the following precautions:

  1. The system must have full charge of refrigerant.

2. Expansion valve adjustment cannot be hurried.

3. Allow sufficient time for the valves to react after each adjustment.

4. Sufficient time must be allowed after each valve adjustment to allow the thermometers to register the true temperatures.

5. The compressor must be operating con tenuously, with a constant discharge pressure.

6. All evaporators must be in operation.

7. Because of the peculiarities of some applications, the system may not respond to the thermostatic expansion valve adjustment out lined. Special consideration must be given to such cases.

NOTE. Under normal conditions, the superheat setting of an expansion valve does not get out of adjustment. When the equipment is originally installed, the installation is under the supervision of a refrigerating engineer. The practice of experimenting with the superheat setting of the expansion valve should be discouraged. This setting should not be changed until all other possible troubles in the system have been eliminated.

 
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